Casting copper cakes



y*Patented Mar. 28, 1939 PATENT OFFICE 2,151,811 cAsTlNG COPPER. oms

Milburn Leo Dorris, Collinsville, Ill., assignor to Braden Copper Company, a corporation of Mame - Application April 29, 1937; serial No. 139,648 1 claim. (ci. zz-zlz) from the casting during solidiflcation. The areas aieoted by these exudations vary with the size of the casting ahd the method of casting. This surface irregularity is' from one-sixteenth to threesixteenths'of an inch in thickness and in severe cases affects asmuch as one-fourth the surface of the entire cake.

Unless these imperfections (sweat) are removed before rolling the cake into sheets, the surface of the sheets corresponding to the affected areas of the cake have lines known as tiger streaks which render the sheets incapable of acquiring a satisfactory high polish. The imperfections maybe mechanically removed from the cake, as for example by a scalping operation, vbut this does not remove the brittle surface remaining under the affected areas. Thus, it frequently happens that sheet copper rolled from` cakes from which "sweat marks have been re-l moved still show the tiger streak surfaces and in vsome instances cracks between the crystals, with resultant breaking of the sheet during deep drawing operations. y

Copper refiners agree that sweat -is a defect that should be eliminated, that is not permitted to occur, not only to avoid the cost of removal but to preclude any possibility of other diiculties arising in the ultimate fabrication of the copper. Various expedients have heretofore been suggested for preventing sweat. For example, water-cooled moulds have been proposed, but under ordinary commercial operating conditions, casting large tonnages on the usual types of casting machines, this has not proved practical. Changing the casting shapes has resulted in some improvement, but is limited to the requirements of the customers. Employing separate moulds for each shape, in lieu of casting several different sizes in the same mould poured to different depths, partially eliminates the trouble, but has the disadvantage of higher mould costs and interruptions caused by changing moulds for small lots of copper.

The present invention aims to prevent the occurrence of sweat in casting copper cakes, and

to this end the invention involves establishing a relatively cool gaseous atmosphere about the faces of the solidifying cake in the initial stages of solidiiication. vI have found that the presence of this relatively cool gaseous atmosphere in contact with the. solidifying cake produces a crust on the surface of the cake that effectively inhibits exudation of the still\molten copper in the interior of the cake. The gaseous atmosphere may advantageously be established about the solidifying cake by enveloping the cake in the initial stage of solidiiication with relatively cool air in any appropriate manner.

In the Aaccompanying drawing, the single iigure diagrammatically illustrates the application to the casting of a wedge cake of refined copper of which I now consider the preferred mode of practicing the present invention. 20

The mould l is of conventional form, and a solidifying cake of copper 2 is shown in the wedgeshaped mould pocket or cavity. After the molten copper has been poured into the mold cavity andy the cake has begunto set, compressed air is applied through 'two or more nozzles 3 to the opposite sides ofthe mould slightly above the top of the copper in the mould. The oppositely-positioned nozzles 3 fit snugly into the `sides of the mould, and to this end the spread between the two nozzles (or parallel sets of nozzles) exceeds the width of the mould cavity by about onequarter inch. Compressed air is supplied to the nozzles through a high pressure line 4, provided with a valve 5 for controlling the volume of air supplied.

In practicing the invention as illustrated in the drawing, the air is turned on gradually until the copper is seen to contract or shrink away from the mould, and the air supply is then increased 40 until a good volume of air is introduced into the small space formedbetween the solidifying copper cake and the adjacent mould side walls as the cake contracts in the initial stage of solidilcation. This application of relatively cool compressed air to the inside of the mould and between the inner mould wall and the copper cake during incipient shrinkage or contraction of the copper in the mould envelopes the solidiyfyingv cake in an atmosphere of relatively cool air andrforms a sur- 5o Y face crust on the solidifying cake through which molten copper does not exude. When solidlcation is complete, the cake is removed from the mould and will be found to be free of "sweat and similar surface imperfections. f

The time for applying the compressed air or other gas to the solidifying cake, after the copper has been poured into the mould, will depend upon the shape of the casting, the speed of pouring, and general casting conditions. This can easily be determined by simple tests under particular operating conditions. In general, the supply of the gas should be commenced as soon as the copper begins to contract or shrink away from the mould, or as soon as the cake contracts in the initial stage of solidifcation to form a space between the inner walls of the mould cavity and the adjacent faces of the cake. Care must be exercised during the application of the gas to the solidifying cake to prevent injury to the partially solidified top or set surface of the casting.

The invention may be practiced in various types of apparatus. and the enveloping of the solidifying copper cake with an atmosphere of relatively cool gas may be effected by various manipulations without departing from the spirit of the invention I claim:

The improvement in casting copper cakes which comprises pouring molten copper into a suitable mold, and immediately after the metal has been completely poured, introducing a, compressed cooling gas into the mold at a point adjacent the upper surface of the cake in order to form a surface crust on the solidifying cake through which the molten copper does not exude, thereby causing the said gas to pass downwardly between the inner walls of the mold and the adjacent faces of the solidifying copper cake as the cake contracts due to cooling.

MILBURN LEO DORRIS. 

